The goal of this application is to examine how rhinovirus (RV) infection induces worsening of asthma. The studies address the discordance between epidemiologic studies showing that RV infection is a common precipitant of asthma exacerbations and clinical studies showing that RV inoculation of asthmatic subjects consistently causes symptoms of a "cold." sometimes cause subtle changes in pulmonary function and in lower airway inflammation, but rarely causes actual asthma exacerbations. Our central hypothesis is that the nature and intensity of the response to RV infection is determined by properties inherent to the infecting strain and/or to the epithelial cells infected. Project 1 (J Widdicombe, Project Leader) will examine the effects of infection with different strains of RV on the structure, function, and mediator production of well-characterized airway epithelial cells cultured at an air-liquid interface. This project will also examine the response to RV infection of cultures of nasal and bronchial epithelial cells obtained from people with and without allergic airway disease, and from nasal and bronchial epithelial cells obtained from people with and without allergic airway disease, and from people with different clinical responses to RV infection. Project 2 (H. Boushey) will obtain RV's by culturing nasal secretions from patients with acute asthma exacerbations and from asthmatic subjects followed prospectively. We will also characterize the clinical and inflammatory responses of the upper and lower airways to infection. This project will further compare the clinical responses to inoculation with two strains of RV16 that differ in their in vitro effects on epithelial cells. It will also provide (to Project 1) nasal and bronchial epithelial cells from subjects characterized as to allergic airway disease and responsiveness to RV infection. Project (R. WU) will conduct array studies of changes in gene expression induced by RV16 infection of bronchial epithelial cells and will compare the patterns of change induced by closely related strains of RV that differ in their in vitro and clinical effects. The Virology Core (D. Schnurr) will culture, isolate, identify, and titrate RV's obtained from infected subjects or epithelial cells, will serially passage RV16 for studies of strain-specific effects of infection, and will sequence these strains to identify genetic sites accounting for strain-specific differences in activity. The Quantitative Genetics Core (C. Dolganolv) will quantify changes in large numbers of selected genes in epithelial cells infected in vitro and in vivo in the three projects proposed. Through this integrated approach, we hope to identify critical determinants of the effects of RV infection in people with asthma, and thus to suggest potential new approaches to prevention and treatment.